DUN HORSES.—Although Mr Darwin gives his address, and I might therefore writer to him direct, I prefer availing myself of THE FIELD, as the subject may be interesting to other parties also. I was some time ago requested to get similar information, and the result was as follows:—The dun and mouse-coloured or eel-backed horses or ponies are common in Norway, and have a dark stripe down the spine, but have no transverse stripe on the shoulders; still one or two people say they have seen the latter, though very rarely and very indistinctly. The cross bars on the legs are general. The marks are not so distinct in the colts when they have their first hair, but as soon as that is cast the marks are very plain, and continue during the animal's life. The mouse-coloured ponies are gradually becoming more rare, the colour not being liked, though they are in general excellent horses. However, when a mouse-coloured pony is crossed with one of a different colour the mouse-colour is strongly inherited, and the colts have the marks on the back and legs. The thorough-bred chesnut ponies have not the marks, but the half-bred chesnuts and light-coloured chesnuts sometimes have them. The brown ponies also frequently have the same stripe on the spine—more frequently than the chesnut—but not on the legs. I subjoin the translation of an article written on the subject by Professor Böeck:—"In the mountainous districts on the western side of Norway, viz., Stavanger, both the upper and lower parts of the province of Bergen, and part of the province of Romsdal, I imagine that the purest race of Norwegian horses is met with—a real Norwegian full blood race. In these countries more horses are bred than are required for use; a considerable number are therefore exported. The inhabitants of these districts have thus had no object in importing foreign horses, and as the race of horses which they possessed was much sought after both by the other districts of Norway and by Sweden, there has been no object in crossing the breed with any other. It is thus to be supposed that the horses existing in these parts of Norway are pure descendants from those brought in by the immigrants to the country. This becomes more probable on remarking the Icelandic horses, which were imported from Norway by the first immigrants, and are exactly like the horses in the mountainous districts of the western part of Norway. The original colour of the Norwegian horse I imagine to be the 'borkede.' [Much the same as is called in England cream colour.] The principal colour is a mixture of yellowish-white, grey, and brown. This colour may change to a yellowish-white, or to a brown, or to a mouse-grey (slate colour), which are the principal colours that are found in the western districts. The pure 'borkede' horse has a black mane and tail, and a black stripe connecting them. The hoofs and legs to the hough joints and fore knee joints are black, and behind the knee are several black transverse stripes. The outer hair of the mane and tail is more frequently light-coloured—even white. The offspring of a cross between the brown and the 'borkede' would be a brown horse with black mane, tail, and legs, though the stripe or eel on the back is often indistinct. The 'borkede' colour may be retained, but the white hair in the mane and tail entirely supersedes the black, so that the mane and tail become altogether white, the stripe on the back and the black hair on the legs are totally los. This is called the 'blakke' colour. Should the 'borkede' colour be paler, the iris of the eye is also light. The offspring of a cross between the grey and the 'borkede' would be the mouse-coloured grey, on which the blackness of the mane, tail, eel, and legs would be less visible, so that the colour of the whole body is nearly the same. Occasional instances are seen when the mouse-grey has a blackish head. Before the colt has changed its first hair the colour of the 'borkede' horse all over the body is nearly the same. The characteristic marks do not appear plain until afterwards, but they continue until old age. The stripes across the shoulders, as on the ass, I have never observed. [This is an answer to a question put to the Professor.] Should the 'borkede' horse—mare or stallion—be crossed with horses of other Norwegian breeds, the offspring would often be the 'borkede,' or it would have the characteristic appearances of the 'borkede' breed in the next generation; however, it is generally noticed that the transverse stripes on the fore legs are lost by such a cross, even if the 'borkede' colour in other respects should be retained. The offspring of a crossed breed often has marks, such as a blaze on the fore-head or nose, white socks, &c. If, therefore, one meets with the 'borkede' horse having any such mark, or wanting the transverse stripes, one can be quite certain that it is not of pure blood.—(Signed) Christian Böeck Professor of Physiology and Veterinary Medicine at the University of Christiania." Professor Böeck, in his letter inclosing the above to me, said he should be happy to give any other information that lay in his power. If, therefore, Mr Darwin wishes for more, and will put his questions in a direct manner, I will endeavour to get them answered. I may also add that I have sent many of the above-described cream-coloured ponies to England; and, as I have lately put myself in correspondence with one of the best districts of Norway for procuring them, I shall be happy to execute any commissions that may be sent to me.—T. BENNETT (Christiania).